You never know what's going to show up in your inbox. Today, out of nowhere, someone sent me a question about the relationship between elliptical and spiral galaxies and whether one turns into the other. Since it's a good question and the response shows the interrelatedness of different parts of astronomy, I figured I'd post the response.

As a refresher to the average SETIzen, a spiral galaxy looks like this:

and an elliptical galaxy looks like this:

There are a lot of differences between elliptical galaxies and spirals, but I'm only going to discuss one here. And, of course, what I'm saying isn't exactly accurate because I'm using a language besides math.

Here's the question:

... if the energy levels of [stars in] elliptical galaxies were generally higher than those of a spiral galaxies, could ellipticals "decay" to become spirals?

Here's my answer:

We do think about galaxies in terms of energy, but a better analogy might be temperature. An elliptical galaxy is "hot", all the stars are orbiting in random directions the way atoms in a hot gas move. A spiral is "cold", with most of the stars orbiting in the same direction at roughly the same speed. In the current epoch, galaxies tend to evolve from "cold" to "hot." When galaxies merge, the energy of the collision tends to go toward randomizing the orbits of the stars, and so you will probably end up with an elliptical galaxy after you've had a bunch of mergers. The centers of dense galaxy clusters tend to contain giant elliptical galaxies that are probably the result of mergers of hundreds of galaxies. These processes are often the subject of supercomputer modeling efforts.

If the Milkyway and the Andromeda galaxy merge, the result will probably be an elliptical galaxy.

It's harder for galaxies to evolve the other direction, because it's hard to get rid of the accumulated energy. An atom with an electron in a high energy level can emit a photon in order to get rid of the energy, but the only thing a galaxy can emit in order to get rid of excess energy is stars. And they do emit stars, but it's hard to put very much energy into a single star so the process is fairly slow. It's similar to evaporation. In an evaporating liquid, the fast moving atoms in the liquid can escape, which removes energy from the liquid, causing it to cool. In an elliptical galaxy, if three or more stars make a close approach to one another, one of the stars might get accelerated to high speed, while the remaining ones slow down.

If the fast star is fast enough, it might be moving at a speed greater than the galaxy's escape velocity. If it escapes, it'll take its kinetic energy with it, which will "cool" the galaxy slightly. Because the remaining stars aren't moving as quickly the galaxy will shrink slightly.

Because this process requires close approaches between stars, it happens most quickly where the stars are the closest together, which is in the center of the galaxy (the core). This causes the core to lose energy rapidly, which causes it to shrink, and if the remaining stars get close enough together, you might form a supermassive black hole. We do tend to find supermassive black holes in the
centers of most every galaxy large, and this may be how they form.

Given enough time (hundreds or thousands of times the current age of the universe), you'll probably end up with a large fraction of the stars having fallen into the black hole, and the rest scattered throughout intergalactic space. @SETIEric

Which type of Galaxy is more likely to contain planets, in the habitable zone, with biological life, that has evolved intelligence, that has learned to use radio, that might be capable of transmitting in our direction?

I would speculate that the spiral galaxy might be more likely, but its just a guess. I bet there is plenty of life in both types. I bet there is lots of life in both those pictures you posted!

Ellipical galaxies have been stripped of all of their gas and dust, so there is little or no new star formation in them. The stars they contain tend to be old and faint. Since (we think) planet formation requires a high abundance of heavy elements that are made in stars, whether there are planets depends on how long ago the gas and dust was stripped.

Spiral galaxies have lots of gas and dust and star formation is still going on in most of them, so the heave element abundance tends to be higher. So you're probably more likely to find planets in spirals. And if planets are necessary for life, that would make spiral galaxies a better place to look.

And if planets are necessary for life, that would make spiral galaxies a better place to look.

You seem to be in agreement that the search for life can be narrowed down by eliminating "Less likely" places where life might exist. In this case, the spiral might be a better place to focus the SETI@home search.

Using this same logic, could SETI@home narrow its search by eliminating data recorded from Hugh chunks of the sky. Using Matt and Jeff's new NitPicker data and the information in the Hipparcos Star Catalog that you have installed on the SETI servers, you could narrow the search.

Am i correct in saying that ALL the data recorded from the whole sky at Arecibo is turned into work units? That means that 95% of the work units are data recorded from parts of the sky with massively distant stars and Galaxy's that any signal would be too faint to detect. There would also be Hugh amounts of data from blank or almost empty parts of the sky. Could we use the information in the Hipparcos Star Catalog to narrow the search to stars and Galaxy's that might be more likely candidates?

Looking at this as an optimist, Contained within the data recorded in the last 10 years are radio transmissions by other intelligent life, but we don't know how strong the signals are and we don't know what frequency they are transmitted on. We also don't know where in the sky the strongest signals are coming from. We need to take the data we have and look closer at the data. Narrow the search and look for fainter signals coming from stars and Galaxy's much closer to home. Who wrote the cosmological book that says that aliens must transmit at 1.42 GHz?. Yes, the hydrogen line is a defined mathematical line in the spectrum, but the spectrum is wide and holds the key to finding what we are looking for.

Q. IF - when one is in 'Space' - why is it that one cannot 'judge' Distance?

> an 'object' may well be quite a distance away from the viewer - as opposed to the Fact that it may well be quite close

Why [?] is this [?]

I'll give a shot at an explanation for this...

The way distances are judged optically is through the process of triangulation. The human mind (and animals' too) does this by forming a mental triangle between the view of an object from one eye vs the view from the other eye, and getting a more or less accurate distance result. Accuracy from triangulation is increased by having a larger angle between the object and view-1/view-2. Unfortunately (or perhaps not), the Human head can only be so large and there is a limit to the size of that angle...the distance between the two eyes.

As objects get farther away from the viewer, the angle between the object and each of the viewer's eyes decreases. At some point it becomes so small it is effectively zero. At that point, the only way to judge distances is to make a guess as to how big something is and estimate based on that guess...not very accurate. The guess is more accurate if you have an object of a known size nearby to the target object and can compare relative sizes. In space, this is not possible.

Most of us have been in a situation where we look at a scene and think that there is this huge object way far away from us...until we realize that the object is actually much smaller and closer than we originally thought. This happens with airplanes, birds, and flying saucers all the time (just kidding about the flying saucers...).

Am i correct in saying that ALL the data recorded from the whole sky at Arecibo is turned into work units? That means that 95% of the work units are data recorded from parts of the sky with massively distant stars and Galaxy's that any signal would be too faint to detect. There would also be Hugh amounts of data from blank or almost empty parts of the sky. Could we use the information in the Hipparcos Star Catalog to narrow the search to stars and Galaxy's that might be more likely candidates?

By not scanning those empty parts of the sky, would we be eliminating the possibility of receiving a signal from a probe launched by a civilization seeking to make contact?
I'm thinking there is the possibility that another lifeform might be seeking contact in a more proactive way than relying on intercepting stray radio broadcasts from a homeworld.

By not scanning those empty parts of the sky, would we be eliminating the possibility of receiving a signal...

Indeed so.

However, note that the search task is infinite to do a completely thorough search (assuming our universe to be infinite). We have limited capability and limited resources to make any search and so only the best of what can be done at the moment is being done. Also, that 'best' relies on various guesses and assumptions.

There has long been hopes of getting data from the Parkes radio telescope in Australia to give coverage of the southern skies. I guess no grants and no progress for that one so far...

Keep searchin',
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Robert & ML1,
What i am suggesting is kinda like what they are doing with the Kepler telescope. NASA knows there is probably tonnes of life out there, but they are not searching the whole 360 degree view of the sky. No, instead with Kepler they are focusing in on one tiny part of the sky so they can take it one step at a time. The theory being;
1. First, lets first find planets! (With Kepler)
2. When we know where the planet is, then we build another telescope to look closer for signs of ozone and atmosphere or biological life.(10 years from now)
3. Then we build another telescope to look even closer to image the actual planet. (20 years from now)
4. When we finally find the planet, with the biological life, we then figure out how to build a spaceship that can travel there. (50 or 100 years from now)

The NASA theory; Lets break down the problem and take it one step at a time!

********

Applying this theory to SETI@home, i am suggesting that so far SETI@home has detected nothing. So yes, ET could well be signalling us right now from 100,000 light years away, but we have no way of detecting it. I'm saying we should do what Kepler is doing by excluding 90% or 95% of the field of view of Arecibo and focus much much closer on the parts of the sky, in the MilkyWay, with large amounts of stars close to us. We have the current computing power to look at this data in massive detail, with more complex algorithms, looking at a wider frequency range, and more of the radio wave part of the electromagnetic spectrum.

In effect we would be looking for ET much closer to home in much greater detail.

If your looking for a needle in a haystack, is it best to stand back and keep scanning the entire haystack with your eyes over and over again. Or is it better to get down on your hands and knees, and start studying small sections of the haystack in much greater detail section by section, hence breaking down the problem.

In fact, the Kepler "Field of view" would actually be a very good general area of sky for SETI@home to focus on as its looking straight down one of the spiral arms of the MilkyWay in the Cygnus constellation;

Kepler "Field of view";

Intelligent Life has already occurred in the MilkyWay, us! so the MilkyWay is a good place to look for Intelligent life. If ET is transmitting, he is doing it right now as we speak, and Arecibo is recording it. But if the signal is very very faint, SETI@home algorithms will not pick it up. But SETI@home can detect it if its algorithms are more precise and focused on a smaller amount of recorded data.

And another point,
I believe this SETI@home project can actually succeed, not in computer science, but in detecting other intelligent life. But it can only do this if the scientists learn from the results its getting. That means this project should evolve as time goes on. If this happens, then without any doubt, this project will succeed and the scientists, Dr. Eric Korpela, Dan Werthimer, Dr. David Anderson, Matt Lebofsky, Jeff Cobb and the others will receive Nobel prizes for exceptional scientific research and their contribution to Mankind. They will have changed all our lives for the better!

These scientists names, and this project will be written down in the history books as one of Mankind's greatest achievements! And 10 million volunteers can feel very proud they were part of this search.

I would like to contribute to this thread by passing along some exciting science news dated today ... Thursday, August 13, 2009 from ... The Allen Telescope Array

Thursday, August 13, 2009

First Results From The Allen Telescope Array

No word from ET (yet) but some useful data that could help solve one the great mysteries about star formation.

The Allen Telescope Array, a joint operation between the SETI Institute in Mountain View and the University of California, Berkeley

The highlight is the images it has made of the movement of atomic hydrogen clouds in the intergalactic space between nearby galaxies, which could help solve one of the big mysteries of star formation.

Many galaxies do not appear to contain enough gas to sustain star formation in the way astronomers expect. That's a puzzle but atomic hydrogen may be the solution. Astronomers do not include atomic hydrogen gas in the reservoir from which they make their calculations because the gas is found largely in intergalactic regions where star formation does not take place.

What the Allen Array team are looking for is evidence that atomic hydrogen clouds are sucked into star forming regions of galaxies where they can contribute to stellar formation.

That's interesting stuff and may yield some fascinating results in the near future.

Eric , I'm I correct ... that you and Dan are contributing scientific code to The Allen Telescope Array ??

Hi Byron,

Haven't heard from you in a while. Hope you're doing well. Dan is heavily involved with the instrumentation for the ATA. Whether that is code depends on where you draw the lines. I'd call it code, but Dan (coming from an electrical engineering background) might disagree. My contribution to that has been minuscule thus far.

Applying this theory to SETI@home, i am suggesting that so far SETI@home has detected nothing. So yes, ET could well be signalling us right now from 100,000 light years away, but we have no way of detecting it.

Not to confuse the issue with facts, but if ET is signaling us "right now" and they're signaling using Radio (since SETI@Home is looking for radio signals) and they're 100,000 light years away, the signal won't get here for 100,000 years.

As we earthlings have evolved, we've gone from blasting "I Love Lucy" all over the galaxy to increasingly controlled emissions, and to a large extent, have installed great ruddy networks of coax and fiber to carry what used to go through the air.

Seems like we need to find a civilization "x" light years away, that was at the proper period in their technological evolution "x" years ago to be beaming "I Love Lintilla" to the stars.

Not to confuse the issue with facts, but if ET is signalling us "right now" and they're signalling using Radio (since SETI@Home is looking for radio signals) and they're 100,000 light years away, the signal won't get here for 100,000 years.

I'm not confused Ned, I'm aware of the speed of light. So it must be taken for granted that anything we measure in electromagnetic spectrum has a time lag proportional to its distance from earth.

I also don't think the simple science concept behind SETI@home has changed, even though human science has progressed. SETI@home is looking at the radio wave part of the spectrum, but its only looking for something around the hydrogen line at 1420 MHz. If (100,000 years ago Ned) ET is broadcasting to us at 100.00 FM, 100 MHz, your favourite radio station, SETI@home won't pick it up. One thousand years from now, we as humans will still know that simple radio waves travel well in space and its still going to be a good way to detect other intelligent life. (Yes, its very complex to listen for ET in the lower wave lengths because of Human RFI).

So my suggestion is focusing on a much smaller, and more specific targeted part of the sky and broadening the search algorithms.

Think about this, the earth is spinning, so Arecibo is only ever "Flashing momentarily" past any single part of the sky as it records. So even if we get 50 recordings from one spot in the sky over 10 years, the recordings for that spot on the sky are still minuscule. Kepler is looking at one small densely populated, targeted part of the sky continuously for 4 years straight, with out blinking. SETI@home does not need to look at one spot for 4 years, but the concept should be similar, targeted searches.

After 10 years searching, we don't call it a day and say there is no ET when all we have measured was a quick flash past the whole sky. No, instead this project evolves and learns from the current zero result.

When NASA took loads of images with Hubble, did NASA call it a day and say there are no planets out there because Hubble did not see them? No, they had a zero result for planets, they evolved the science and progressed. They built Kepler, the first of several steps to finding biological life on another planet.

And thanks Byron, its interesting to see the SETI Institute, and the ATA, both ET projects, are publishing science papers about real science. I bet the NSF will look very kindly on these scientists when it comes to funding. It goes to show you that you can look for ET and get NSF funding if your clever. Byron its also worth noting the hugh emphasis on the seti institute website on "Educating Kids" and "Kids Science". The NSF just love that stuff, they love to see scientists educating Kids, they throw money at that kind of stuff. Just a few pages of "Kids" science and the NSF are happy campers.(I would be glad to volunteer to prepare some kids science pages if needed (Eric, PM me if you need)).

Not to confuse the issue with facts, but if ET is signalling us "right now" and they're signalling using Radio (since SETI@Home is looking for radio signals) and they're 100,000 light years away, the signal won't get here for 100,000 years.

I'm not confused Ned, I'm aware of the speed of light. So it must be taken for granted that anything we measure in electromagnetic spectrum has a time lag proportional to its distance from earth.

I also don't think the simple science concept behind SETI@home has changed, even though human science has progressed. SETI@home is looking at the radio wave part of the spectrum, but its only looking for something around the hydrogen line at 1420 MHz. If (100,000 years ago Ned) ET is broadcasting to us at 100.00 FM, 100 MHz, your favourite radio station, SETI@home won't pick it up. One thousand years from now, we as humans will still know that simple radio waves travel well in space and its still going to be a good way to detect other intelligent life. (Yes, its very complex to listen for ET in the lower wave lengths because of Human RFI).

So my suggestion is focusing on a much smaller, and more specific targeted part of the sky and broadening the search algorithms.

Arecibo is much more "steerable" than you'd think, but the problem isn't the ability (or inability) to control the telescope from a technical standpoint.

It's organizational.

The data for SETI@Home comes from SERENDIP. The basic idea there is that the cost of time where you control the telescope is expensive, so instead of demanding control of the telescope, you stick another receiver at the feed and go along for the ride while someone else pays to control the telescope.

SETI@Home gets signals from the ALFA receiver, which was built by a consortium to spread costs.

Listening at 100 MHz would require a different receiver, with a different feed antenna (the dish at Arecibo would be fine, just the resonant elements at the feed itself).

So, as with many things, there is a difference between what you'd like to do, and what you can do.

1420 MHz was chosen because it's a quiet spot in the radio spectrum, at least observed from here. When tuning around looking for a place to transmit, you look for a quiet spot -- the noisy spots take a lot more transmit power to get above the noise. Is that the best spot? Who knows.

A new study found that the earliest black holes lacked nearby matter to gobble up, and so lay relatively stagnant in pockets of emptiness.

The finding, based on the most detailed computer simulations to date, counters earlier ideas that these first black holes accumulated mass quickly and ballooned into the supermassive black holes that lurk at the centers of many galaxies today.

"It has been speculated that these first black holes were seeds and accreted huge amounts of matter," said the study's leader Marcelo Alvarez, an astrophysicist at the Kavli Institute for Particle Astrophysics and Cosmology in California. "We're just finding out that it could be much more complex than that."

Alvarez and colleagues constructed a computer simulation of the early universe based on measurements of the cosmic background radiation left over from the Big Bang, which scientists think started the universe 13.7 billion years ago. The model used these starting conditions, and the laws of physics, to watch how the universe may have evolved.

The study is detailed in an upcoming issue of The Astrophysical Journal Letters. The Kavli Institute is at the Stanford Linear Accelerator Center (SLAC) National Accelerator Laboratory in Menlo Park, Calif.

Hungry, hungry black holes

In the simulated young universe, clouds of gas condensed to form the first stars. Because of the chemistry of the gas at this time, these stars were much larger than today's typical stars and weighed more than a hundred times the mass of the sun.

After a short time these massive, hot stars exhausted their internal fuel and collapsed under their own immense weight to form black holes. But because the huge stars had emitted such strong radiation when they were still alive, they had blown most nearby gas away and left very little matter to be eaten by the resulting black holes.

Rather than swiftly swallowing large chunks of matter and growing into larger black holes, the simulation showed that the universe's first black holes grew by less than one percent of their original mass over the course of a hundred million years.

The scientists don't know what eventually became of these hungry black holes.

"It is possible that they merged onto larger objects that then themselves collapsed into black holes, bringing these first black holes along for the ride," Alvarez told SPACE.com. "Another possibility is that they got kicked out of the galaxy by interactions with other objects and would just be floating around in the halo of the galaxy now."

Whatever happened, the researchers think that these trailblazing black holes may have played an important part in shaping the evolution of the first galaxies.

Even on a diet, the black holes likely produced significant amounts of X-ray radiation, which is released when mass falls onto a black hole. This radiation could have reached gas even at a distance and heated it up to temperatures too high to condense and form stars. Thus the first black holes may have prevented star formation in their vicinity.

These hot gas clouds may have carried on for millions of years without creating stars, and then eventually collapsed under their own weight to create supermassive black holes.

Though this idea is only speculation, the researchers are intrigued by the possible effects of the universe's first black holes.

"This work will likely make people rethink how the radiation from these black holes affected the surrounding environment," said John Wise of NASA Goddard Space Flight Center in Greenbelt, Md. "Black holes are not just dead pieces of matter; they actually affect other parts of the galaxy."

For the waiting world, and indeed for most of us here at CERN, ‘the LHC schedule’ simply means the date that the LHC will restart - and we only take notice when that end-date changes. But in fact the schedule is a constantly evolving intricate document coordinating all the repairs, consolidation and commissioning in every part of the machine. So, what actually goes on behind the scenes in timing and planning all the work on one of the most complex scientific instruments ever built?